Argyroderma testiculare

Argyroderma testiculare is a small perennial succulent in the Aizoaceae family. It comes from the Vanrhynsdorp district of South Africa’s Western Cape. It grows among pebbles on flat ground strewn with quartz. Its wider habitat falls within desert or dry shrubland. Wild plants occur at elevations of 394–1,312 feet [120–400 metres]. This species is not native to Britain or Ireland.

The plant has a compact form with paired, thick leaves. Some plants branch and make short columns. Each leaf has a half-oval shape and a clear keel. Leaves measure about 0.08–0.11 feet [0.025–0.035 metres] long. They sit close together, with a small gap between their tips. Young foliage is dark green. Old leaf pairs turn yellow, then black, but stay attached. These old leaves form a close bowl around the new foliage. This lasting layer helps give the plant its distinct form.

Single flowers sit on very short stalks or almost none. Each bloom spans about 0.08–0.11 feet [0.025–0.035 metres]. Most flowers are deep purple. Pink, white and yellow flowers also occur, but less often. Flower colour can differ within the same wild population. The inner petals are often shorter than the outer ones. In its native range, flowering starts in April. Northern Hemisphere plants flower mainly in August. Fruits and new leaves develop during the rainy season. The fruits are hygrochastic capsules, which open when wet. They stay on the parent plant and contain smooth brown seeds.

In cultivation, give this plant full sun and very sharp drainage. Keep it cool with shade during summer. Too little light makes the plant’s body thinner. A gritty, mineral-rich mix with an acidic reaction suits it. Water needs are low, and summer watering should be rare. Give summer water only when the plant begins to shrivel. Excess water can split the skin and leave scars. The plant is also prone to rot. LLIFLE reports cold tolerance near −5°C, with differences between clones.

Use diluted, potassium-rich feed in modest amounts during active growth. Propagate by seed or by dividing larger clumps. Seeds can sprout within one to two weeks at 21°C. Cuttings are harder to root. The supplied evidence gives no species-specific information on food use or toxicity.